Pilot studies will be performed which will provide data useful for the study of the structure and biochemistry of the calcitonin receptor. The calcitonin receptor will be radioactively labeled using photoaffinity analogs of calcitonin and chemical crosslinking agents. The radiolabeled receptor will be purified from detergent extracts of cell membranes. The development of monoclonal antibodies to the calcitonin receptor will be initiated. With more basic information about the calcitonin receptor, it will be possible later to investigate in greater detail the features of osteoclast function and differentiation, to define better the role of calcitonin in normal human bone remodeling, and to determine whether calcitonin deficiency may be important in the pathophysiology of osteoporosis.